Behavioral studies of the sensitive periods of development of visual functions in monkeys.
The age-dependent effects of monocular form deprivation on psychophysically determined visual functions were investigated in rhesus monkeys. Monocular form deprivation was initiated at various ages from 1 to 25 months and maintained for 18 months. The effects of form deprivation varied across the visual functions evaluated. Absolute scotopic sensitivity was depressed by form deprivation initiated only at 1 or 2 months of age. Photopic, increment-threshold spectral sensitivity functions showed alterations in sensitivity levels for monkeys treated at 5 months of age or earlier, with no effect thereafter. Monocular form deprivation at 1 to 5 months of age resulted in profound deficits in spatial modulation sensitivity. The effects on spatial vision decreased systematically as the age of onset was delayed from age 6 to 18 months. Finally, binocular summation measures revealed an absence of binocular vision even for the monkey form-deprived at 25 months of age, i.e. the experimental treatment series failed to define the upper limit of the age-range for the effects of monocular form deprivation on binocular summation mechanisms. Comparisons of the age-dependent effects of monocular form deprivation across the various functions demonstrated that the sensitive period, i.e. the period of life during which a visual function may be altered by monocular form deprivation, was different for each of the psychophysical measures of visual function.
Harwerth
R S
RS
College of Optometry, University of Houston, TX 77204-6052.
Smith
E L
EL
Crawford
M L
ML
von Noorden
G K
GK
D000818:Animals; D003118:Color Perception / Q000502:physiology; D003423:Critical Period, Psychological; D004292:Dominance, Cerebral / Q000502:physiology; D008253:Macaca mulatta; D008297:Male; D009473:Neuronal Plasticity / Q000502:physiology*; D010786:Photoreceptor Cells / Q000502:physiology; D011601:Psychophysics; D012029:Refraction, Ocular; D012683:Sensory Deprivation / Q000502:physiology; D012684:Sensory Thresholds / Q000502:physiology; D015348:Vision, Binocular / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*